1. Field of the Invention
The invention relates to a control system that is structured to control a drive power characteristic defined as a relation of an accelerator operation amount to the output of a drive power source, the speed ratio, etc., a suspension characteristic or chassis characteristic defined as the vehicle's cornering (turning) performance responsive to the driver's steering operation, sinking of the outer side wheels at a corner, the degrees of bumps and rebounds, or the ease with which bumps and rebounds occur, etc. (may hereinafter be commonly, or collectively, referred to as “running characteristics”), such that they conform to the driver's preference(s), vehicle travel environment, and so on.
2. Description of Related Art
The manners in which the behavior of a vehicle changes in response to an accelerator operation, a brake operation, a steering wheel operation, etc. depend on the structures of mechanisms related, to such operations, and the data set and used by a control system. In many vehicles, “running characteristics”, that is, the manners in which the behavior of the vehicle body changes in response to, for example, the amounts of operations and external forces input from the tires, are set to characteristics that are most likely to be accepted by customers, taking into account the intended uses of the vehicles and prospective and/or target users.
Running characteristics, individually set for each vehicle model, are set so as to meet conditions prescribed based on expectations and assumptions in design. However, in reality, there are various driver's preferences, and the vehicle travels in various travel environments, such as roads in urban and residential areas, expressways, windings, uphill roads, and downhill roads. Thus, in reality, the characteristics required of the vehicle differ from one driver to another, and from one travel environment to another. Various technologies have been developed to minimize the discrepancies or difference between vehicle characteristics and the driver's driving preference(s). One such technology is described in the following patent documents.
The system described in Japanese Patent Application Publication No. 06-249007 (JP-A-06-249007) is structured to factor the driver's driving preference(s) in the behavior control of the vehicle. More specifically, the system described in Japanese Patent Application Publication No. 06-249007 is a drive power control system using a neurocomputer, and it is structured to learn a relation of an acceleration(s) to the accelerator pedal travel and vehicle speed, formulate “required acceleration model” from the learned relation, and then calculate a throttle opening degree based on the difference between the required acceleration model and “second reference acceleration model” reflecting the driver's driving preference(s) and the difference between the second reference acceleration model and “first reference acceleration model” that is a standard reference acceleration model.
Meanwhile, Japanese Patent Application Publication No. 2008-132876 (JP-A-2008-132876) describes a vehicle control system that includes multiple switches used to select the drive mode from among multiple modes. The switches include a “SPORT” mode switch, a “SNOW” mode switch, and an “ECO” mode switch. When the drive mode is selected through switch operation, the vehicle control system outputs control command signals, including the one indicating the selected drive mode, to an engine ECU and a suspension ECU to operate given actuators in accordance with the selected drive mode.
Further, Japanese Patent Application Publication No. 2008-74229 (JP-A-2008-74229) describes a vehicle travel control system structured to allow the driver to select a desired lateral acceleration. According to this publication, the vehicle travel control system may be structured to switch the lateral acceleration from one value to another value depending upon which of “SPORT” mode and “NORMAL” mode of the automatic transmission is presently set, and further the vehicle travel control system may be structured to switch the lateral acceleration from one value to another value depending upon which of “SPORT” mode and “NORMAL” mode of the suspension mechanisms is presently set, and through such switching, the running can be made “mild” or “agile”.
Further, Published Japanese Translation of PCT Application No. 2009-530166 (JP-A-2009-530166) describes a system that determines the driver's driving style based on the data indicating accelerations in the vehicle, and then sets the operations of sub-systems according to the determined driving style. According to this publication, the sub-systems include an engine control system, transmission control system, steering control system, brake control system, air-suspension control system, etc.
As mentioned earlier, various technologies have been developed which change or set control amounts, etc. for a throttle valve, a suspension mechanism, a transmission, and so on, in accordance with vehicle accelerations or in response to the driver's switch operation, and control the acceleration performance and suspension performance of the vehicle to conform to the present acceleration/deceleration state and driver's driving preference(s). However, there are various factors that affect the acceleration performance, cornering (turning) performance, ride, etc. of the vehicle. In reality, therefore, with related-art technologies as those described above, although one or more of control characteristics that influence the running characteristics of the vehicle, such as the drive power characteristic and chassis characteristic, can be changed according to accelerations or in response to switch operation, expected or desired running characteristics can not be obtained sufficiently.